Other mistake: It's not possible for Holmes to remove all of his elderly bookkeeper disguise in the mere seconds Watson turned his back.
The Return of Sherlock Holmes (1986)
1 other mistake in The Empty House - chronological order
Starring: Jeremy Brett, Rosalie Williams, Edward Hardwicke
Revealing mistake: While Holmes and Watson are investigating the crime scene, there is a shot of them that shows the dead man's hand. His hand is visibly shaking, revealing the actor is struggling to maintain the position of his hand.